Method for recovering high-purity black mass from used lithium ion secondary battery

Abstract

The present invention relates to a method for recovering high-purity black mass from a used lithium ion secondary battery and, more particularly, to a method for recovering high-purity black mass through: an alkaline thermal hydrolysis step of stirring a cell lysate of the used lithium ion secondary battery in an alkaline aqueous solution to dissolve and separate impurities contained in the cell lysate into an aqueous solution; and a low-temperature pyrolysis step of decomposing and removing organic compound components, such as an organic binder.

Description

Method for recovering high-purity black mass from spent lithium-ion secondary batteries

[0001] The present invention relates to a method for recovering high-purity black mass from a used lithium-ion secondary battery, and more specifically, to a method for recovering high-purity black mass through an alkaline thermal hydrolysis step in which impurities contained in the crushed cell material are dissolved and separated into the aqueous solution by stirring the crushed cell material in an alkaline aqueous solution, and a low-temperature thermal decomposition step in which organic compound components such as organic binders are decomposed and removed.

[0002] Lithium-ion secondary batteries are widely used in various fields such as smartphones, electric vehicles, and energy storage systems (ESS), and generally consist of an anode, a cathode, an electrolyte, a separator, and a case. The anode is mainly composed of lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt oxide (LNCM), etc., the cathode is mainly composed of graphite, the electrolyte is composed of lithium salts and organic solvents, the separator is mainly composed of polyethylene (PE) or polypropylene (PP), and the case is composed of aluminum, stainless steel, etc.

[0003] Used lithium-ion rechargeable batteries contain rare and valuable metals such as lithium (Li), cobalt (Co), and nickel (Ni). Recycling allows these resources to be reused, saving the costs and energy required to mine new resources and contributing to the alleviation of resource depletion. Furthermore, given the current situation where regulations regarding the management of used lithium-ion rechargeable batteries are being strengthened in many countries, including Europe and the United States, the recycling of these batteries is crucial from both environmental and economic perspectives. Proper disposal of used lithium-ion rechargeable batteries can reduce environmental pollution and prevent the release of heavy metals and hazardous chemicals into nature.

[0004] The recycling of lithium-ion secondary batteries is classified into a pretreatment process that separates used lithium-ion secondary batteries into a mixture containing valuable metals, and a posttreatment process that refines the separated components and processes them into a final product. The pretreatment process is a necessary step to increase the recycling efficiency of used lithium-ion secondary batteries and generates black mass, which is a mixture containing valuable metals such as lithium, cobalt, and nickel, by removing impurities from the components of the lithium-ion secondary batteries. In addition to valuable metal resources, black mass may contain other impurity components such as aluminum (Al), copper (Cu), iron (Fe), and chromium (Cr).

[0005] However, conventional pretreatment processes for spent lithium-ion secondary batteries recover black mass through simple physical crushing, grinding, and high-temperature heat treatment. Physical methods involving mechanical crushing and separation can result in the loss of recoverable resources, and even after separation, precise sorting is difficult, leading to reduced recycling efficiency due to residual impurities and other contaminants. The high-temperature heat treatment method following crushing and grinding results in high energy consumption and poses a problem of potential damage to some useful materials, which limits the recovery of high-purity black mass.

[0006] The black mass obtained from conventional pretreatment processes lacks established standardization and contains a large amount of impurities, which lowers the recovery rate of valuable metals such as lithium, cobalt, and nickel, and leads to a decline in the quality and productivity of the final products manufactured through posttreatment processes, such as lithium carbonate, lithium hydroxide, cobalt sulfate, and nickel sulfate.

[0007] Meanwhile, Korean registered patent No. 10-2447931 discloses a method for recovering black mass by crushing and heat-treating used lithium-ion secondary battery cells, but it has problems such as high energy consumption due to high-temperature heat treatment, and the inability to recover high-purity black mass because impurities such as aluminum and copper are oxidized and remain in the black mass.

[0008] The present invention aims to provide a method for recovering high-purity black mass by effectively dissolving and separating impurity factors that adversely affect recycling efficiency from used lithium-ion secondary batteries using an alkaline thermal hydrolysis method after crushing the used lithium-ion secondary batteries.

[0009] The present invention also aims to provide a method for recovering high-purity black mass by efficiently decomposing and removing organic compounds, with the effect of reducing energy consumption and carbon dioxide emissions compared to conventional high-temperature heat treatment by applying a low-temperature pyrolysis method after alkaline thermal hydrolysis.

[0010] A method for recovering high-purity black mass from a used lithium-ion secondary battery cell or a component including the same according to the present invention for solving the above problem is a method for recovering high-purity black mass containing lithium (Li) and a transition metal compound such as nickel (Ni), cobalt (Co), manganese (Mn), copper (Cu), iron (Fe), chromium (Cr), or one or more transition metals from a used lithium-ion secondary battery cell or a component including the same, wherein

[0011] (a) A discharge disassembly step of electrically discharging a used lithium-ion secondary battery cell or a component including the same and disassembling it into a final cell form;

[0012] (b) A deposition step of completely discharging the finally decomposed cell in an inert atmosphere;

[0013] (c) A wet crushing step in which a polar protic solvent is mixed and crushed in the cell after the above deposition step to solute the ionic substance within the cell and obtain it in the form of a slurry;

[0014] (d) an alkaline thermal hydrolysis step of stirring the above slurry in an alkaline aqueous solution at a temperature of 20°C to 90°C to dissolve and separate impurities contained in the slurry into the aqueous solution;

[0015] (e) A solid-liquid separation step in which the aqueous solution obtained after the alkaline thermal hydrolysis step is filtered to separate it into a liquid phase in which impurities are dissolved and a solid cake in which impurities are removed;

[0016] (f) a low-temperature pyrolysis step of maintaining the above solid cake in an inert atmosphere at a temperature of 200°C to 450°C for 30 to 200 minutes to obtain a powder form in which organic compound components, such as organic binders, are decomposed and removed;

[0017] (g) A classification step for separating and recovering black mass by vibrating the powder above; is included.

[0018] At this time, the used lithium-ion secondary battery cell or the component including it includes medium-to-large lithium-ion secondary battery cells, modules, packs, and small lithium-ion secondary battery cells, and the slurry obtained in the (c) wet crushing step or the low-purity black mass introduced into the (d) alkaline thermal hydrolysis step is characterized by having a total inorganic component other than transition metals of lithium, nickel, cobalt, and manganese of 200,000 ppm or less, and the high-purity black mass separated and recovered through the (g) classification step has a total inorganic component other than transition metals of lithium, nickel, cobalt, and manganese of 50,000 ppm or less, and the slurry or the low-purity black mass is in the form of LiNi x Co y Mn 1-x-yO2(; here 0 <x<1, 0<y<1)의 리튬니켈코발트 망간산화물을 포함하며, 상기 (d) 알칼리 열가수분해 단계를 통해 용해 분리되는 상기 불순물은 리튬, 니켈, 코발트 및 망간의 전이금속 외의 무기성분과 유기바인더와 같은 유기화합물을 포함할 수 있다.

[0019] Meanwhile, the liquid containing impurities filtered in the above (e) solid-liquid separation step can be reused as process water in the (c) wet crushing step.

[0020] Meanwhile, the above (a) discharge decomposition step may be performed by discharging the residual voltage in the used lithium-ion secondary battery to 15% to 30% using a separate discharger.

[0021] Meanwhile, the above (b) penetration step may include using a gas capable of suppressing oxidative explosion reactions, such as argon (Ar) and nitrogen (N2), and the penetration step of the decomposed cell may be configured to include using a separate penetration jig, wherein the number of penetration holes per cell by the separate penetration jig is 2 to 20, and supplying the gas with a purity of 95% to 99.5% at a flow rate of 10 N㎥ / h to 50 N㎥ / h.

[0022] Meanwhile, the above (c) wet crushing step includes crushing to a size of 0.2 mm to 2.0 mm using one or more of a shredder, cut crusher, and hammer crusher by applying a crushing mechanism of shear and impact according to the shape of the cell, and the polar protic solvent may include water.

[0023] Meanwhile, the above (d) alkaline thermal hydrolysis step uses a strongly alkaline aqueous solution with a pH of 10 to 14, and the impurities dissolved by thermal hydrolysis in the alkaline aqueous solution include one or more of the compounds of aluminum (Al), copper (Cu), iron (Fe), phosphorus (P), fluorine (F), and silicon (Si) which are by-products of the anode material and cathode material and electrolyte components that are constituents of the cell, and the alkaline aqueous solution includes one or more of the strongly alkaline substances such as sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2), and potassium hydroxide (KOH), and the ratio of the slurry to the alkaline aqueous solution can be used as 1:3 to 1:20.

[0024] Meanwhile, the above (e) solid-liquid separation step may be configured to separate the liquid phase containing impurities including one or more of aluminum, phosphorus, fluorine, and silicon compounds and the solid phase cake containing one or more of transition metal compounds such as lithium, nickel, cobalt, manganese, copper, iron, and chromium by using a device for separating the solid phase and the liquid phase, such as a centrifuge, a filter press, and a vacuum filter.

[0025] Meanwhile, the above (f) low-temperature pyrolysis step includes using a gas capable of suppressing oxidative explosion reactions, such as argon (Ar) and nitrogen (N2), in a rotary kiln, wherein the rotary kiln is rotated at a speed of 3 rpm to 30 rpm at an angle of 5 to 30 degrees, and the gas with a purity of 99% to 99.5% is supplied at a flow rate of 10 N㎥ / h to 80 N㎥ / h, and may be configured to facilitate the separation of active materials from aluminum and copper current collectors or to decompose and remove organic compound components such as organic binders.

[0026] Meanwhile, the above (g) classification step may be configured to use a sieve vibrator and a standard sieve to vibrate and separate the primary black mass through standard sieve sieving of 20 mesh to 50 mesh for a time of 10 min to 20 min with an amplitude of 0.5 mm to 1.0 mm, and vibrate and separate the secondary black mass through standard sieve sieving of 60 mesh to 120 mesh for a time of 10 min to 20 min with an amplitude of 1.0 mm to 2.0 mm.

[0027] According to the present invention, after crushing the used lithium-ion secondary battery as described above, a method can be provided to effectively dissolve and separate impurity factors that adversely affect recycling efficiency from the used lithium-ion secondary battery using an alkaline thermal hydrolysis method to recover high-purity black mass.

[0028] According to the present invention, by applying a low-temperature pyrolysis method after the alkaline thermal hydrolysis, it is possible to reduce energy consumption and carbon dioxide emissions compared to conventional high-temperature heat treatment, and to provide a method for recovering high-purity black mass by efficiently decomposing and removing organic compounds.

[0029] FIG. 1 is a flowchart illustrating, in sequence, a method for recovering high-purity black mass from a used lithium-ion secondary battery cell or a component including the same, as an embodiment of the present invention.

[0030] FIG. 2 is a flowchart showing the sequence of a method for recovering black mass from a conventional used lithium-ion secondary battery cell or a component including the same.

[0031] FIG. 3 is an actual image of black mass recovered according to one embodiment of the present invention.

[0032] Figure 4 is a scanning electron microscope (SEM) image at 500x magnification of a black mass recovered according to one embodiment of the present invention.

[0033]

[0034] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. However, embodiments according to the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the art.

[0035] The present invention relates to a method for recovering high-purity black mass from a used lithium-ion secondary battery.

[0036] FIG. 1 is a flowchart showing the sequence of a method for recovering high-purity black mass from a used lithium-ion secondary battery as an embodiment of the present invention.

[0037] Referring to FIG. 1, an embodiment of the present invention comprises: (a) a discharge decomposition step of electrically discharging a used lithium-ion secondary battery cell or a component including the same and decomposing it into a final cell form; (b) a deposition step of completely discharging the finally decomposed cell in an inert atmosphere; (c) a wet crushing step of mixing and crushing a polar protic solvent with the cell after the deposition step to solute ionic substances within the cell and obtain a slurry form; (d) an alkaline thermal hydrolysis step of stirring the slurry in an alkaline aqueous solution at a temperature of 20°C to 90°C to dissolve and separate impurities contained in the slurry into the aqueous solution; and (e) a solid-liquid separation step of filtering the aqueous solution after the alkaline thermal hydrolysis step to separate it into a liquid phase in which impurities are dissolved and a solid cake from which impurities have been removed. (f) a low-temperature pyrolysis step of maintaining the solid cake in an inert atmosphere at a temperature of 200°C to 450°C for 30 to 200 minutes to obtain a powder form in which organic compound components such as organic binders are decomposed and removed; (g) a classification step of separating and recovering black mass by vibrating the powder; the present invention provides a method for recovering high-purity black mass from a used lithium-ion secondary battery, characterized by comprising: (f) a low-temperature pyrolysis step of maintaining the solid cake in an inert atmosphere at a temperature of 200°C to 450°C for 30 to 200 minutes to obtain a powder form in which organic compound components such as organic binders are decomposed and removed; (g) a classification step of separating and recovering black mass by vibrating the powder.

[0038] The following explains the process in order.

[0039]

[0040] (a) Discharge decomposition step;

[0041] First, the residual voltage in the used lithium-ion secondary battery is discharged to 15% to 30% using a separate discharger, and the lithium-ion secondary battery pack that has undergone electrical discharge treatment is disassembled into modules, and the disassembled modules can be finally disassembled into cells.

[0042]

[0043] (b) The excavation stage;

[0044] First, to relieve internal pressure and residual power of the discharged used lithium-ion secondary battery cell and to suppress oxidation explosion reactions, it can be deposited in an argon (Ar) and nitrogen (N2) atmosphere.

[0045] The above argon (Ar) and nitrogen (N2) are supplied using a gas generator, and gas with a purity of 95% to 99.5% can be supplied at a flow rate of 10 N㎥ / h to 50 N㎥ / h. Since the shape of the cell varies depending on the battery manufacturer, one or more tools such as electric drilling and piercing may be used depending on the shape of the cell.

[0046]

[0047] (c) Wet crushing step;

[0048] Next, the ionic material can be obtained in the form of a slurry by wet crushing the cell treated in the (b) deposition step with a polar protic solvent such as water to solute it.

[0049] Depending on the shape of the cell above, a crushing mechanism of shear and impact can be applied, and one or more of a shredder, cut crusher, and hammer crusher can be used to crush the material to a size of 0.2 to 2.0 mm. (b) Wet crushing can be performed by adding 50 to 150 parts by weight of a solvent based on 100 parts by weight of the product of the burrowing step. Wet crushing can be performed for 60 minutes to 240 minutes by adding a solvent at 10°C to 40°C.

[0050]

[0051] (d) Alkaline thermal hydrolysis step;

[0052] Next, (c) alkaline thermal hydrolysis can be performed by thermally decomposing the slurry obtained from the wet crushing step in an alkaline aqueous solution at a temperature of 20 to 90°C to dissolve impurities contained in the slurry into the aqueous solution.

[0053] The above alkaline aqueous solution uses a strongly alkaline aqueous solution with a pH of 10 to 14, and the composition of the alkaline aqueous solution may include one or more of strong alkaline substances such as sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2), and potassium hydroxide (KOH), and the ratio of the slurry to the alkaline aqueous solution may be 1:3 to 1:20. The stirring speed may be 200 rpm to 500 rpm. It is preferable to perform the alkaline thermal hydrolysis process for at least 2 hours so that impurities can be sufficiently dissolved.

[0054] The slurry may contain one or more impurity components, such as aluminum, copper, iron, phosphorus, fluorine, and silicon compounds, in addition to transition metal compounds of lithium, nickel, cobalt, and manganese.

[0055] For example, the reaction mechanism for the dissolution of aluminum, one of the impurity factors, in an aqueous solution through alkaline thermal hydrolysis is as follows.

[0056] Reaction formula (1): 2Al(s) + 2NaOH(s) + 6H2O(l) → 2Na(Al(OH)4)(aq) + 3H2(g)

[0057] Reaction formula (2): 2Al(s) + 2Ca(OH)2(s) + 10H2O(l)→ 2Ca(Al(OH)6)(aq) + 5H2(g)

[0058] Reaction formula (3): 2Al(s) + 2KOH(s) + 2H2O(l) → 2KAlO2(aq) + 3H2(g)

[0059] For example, the reaction mechanism for the dissolution of silicon, one of the impurity factors, in an aqueous solution through alkaline thermal hydrolysis is as follows.

[0060] Reaction equation (4): Si(s) + 2NaOH(s) + H2O(l) → Na2SiO3(aq) + 2H2(g)

[0061] Reaction equation (5): Si(s) + 2KOH(s) + H2O(l) → K2SiO3(ag) + 2H2(g)

[0062]

[0063] (e) High-value separation stage

[0064] Next, (d) by filtering the aqueous solution obtained from the alkaline thermal hydrolysis step to separate the solid and liquid phases, a solid cake with impurities removed can be obtained.

[0065] Solid-liquid separation is not limited to centrifuges, filter presses, vacuum filters, etc., and can be separated into a liquid phase containing impurities including one or more of aluminum, phosphorus, fluorine, and silicon compounds, and a solid phase cake containing one or more of transition metal compounds such as lithium, nickel, cobalt, manganese, copper, iron, and chromium by using a device for separating solid and liquid phases.

[0066]

[0067] (f) Low-temperature pyrolysis stage

[0068] Next, (e) by low-temperature pyrolysis of the solid cake separated in the solid-liquid separation step, a powder from which organic compounds such as organic binders have been removed can be obtained.

[0069] To improve high performance, safety, and cost efficiency, lithium-ion secondary battery cathode materials undergo complex processes such as mixing raw materials including high-purity lithium, cobalt, nickel, and manganese, calcination, coating with conductive materials, and molding with binders. The anode material proceeds through steps similar to the cathode material manufacturing process, except for the difference that graphite is used as a raw material. The electrolyte is manufactured by mixing lithium salts with organic solvents and adding additives to improve performance. For this reason, the solid cake contains organic compounds such as the cathode material, organic binders from the anode material manufacturing process, and organic solvents from the electrolyte, which can act as a factor in reducing the purity of the black mass. By performing low-temperature pyrolysis, energy consumption and carbon dioxide emissions can be reduced compared to conventional high-temperature heat treatment, and organic compounds can be efficiently decomposed and removed.

[0070] The low-temperature pyrolysis process can be performed in an argon (Ar) and nitrogen (N2) atmosphere to suppress phase changes of the metal components remaining in the solid cake.

[0071] The above argon (Ar) and nitrogen (N2) can be supplied using a gas generator, and gas with a purity of 99% to 99.5% can be supplied at a flow rate of 10 N㎥ / h to 80 N㎥ / h.

[0072] The low-temperature pyrolysis process may utilize a rotary kiln. While a non-rotary kiln may be used, a rotary kiln is preferable to filter out as many impurities as possible.

[0073] The above rotary kiln can operate at an angle of 5 to 30 degrees at a rotational speed of 3 to 30 rpm.

[0074] The low-temperature pyrolysis process can be carried out by increasing the temperature at a heating rate of 10℃ / min and maintaining it at a temperature of 200℃ to 450℃ for 30 minutes to 200 minutes. The heating temperature can be controlled depending on the type of organic binder.

[0075] The low-temperature pyrolysis process can facilitate the separation of active materials from aluminum and copper current collectors, or decompose and remove organic compound components such as organic binders like PVDF and organic solvents like EC.

[0076] The types of organic solvents and boiling points of the electrolytes mainly used in battery cell manufacturing are shown in Table 1 below.

[0077] Type EC (Ethylene Carbonate) PC (Propylene Carbonate) DMC (Dimethyl Carbonate) DEC (Diethyl Carbonate) EMC (Ethylmethyl Carbonate) Boiling point (℃) 248241.790126.8108

[0078] The types of additives and boiling points of electrolytes mainly used in battery cell manufacturing are shown in Table 2 below.

[0079]

[0080]

[0081] Type VC (Vinylene Carbonate) FC (Fluoroethylene Carbonate) VEC (Vinyl Ethylene Carbonate) Boiling point (℃) 162212237

[0082] The types of organic binders mainly used in battery cell manufacturing and their decomposition temperatures are shown in Table 3 below.

[0083] Type PVDF (Polyvinylidene Fluoride) PTFE (Polytetrafluoroethylene) SBR (Styrene Butadiene Rubber) CMC (Carboxymethyl Cellulose) Decomposition temperature (℃) 350350~400400168

[0084] (g) Classification stage

[0085] Next, (f) the powder from which organic compound components have been removed in the low-temperature pyrolysis step can be sieved using a sieve vibrator and a standard sieve to recover the final black mass.

[0086] The first classification can be performed by vibrating through a standard sieve of 20 mesh to 50 mesh with an amplitude of 0.5 mm to 1.0 mm for a time of 10 min to 20 min, and the second classification can be performed by vibrating through a standard sieve of 60 mesh to 120 mesh with an amplitude of 1.0 mm to 2.0 mm for a time of 10 min to 20 min.

[0087]

[0088] In the following, the present invention will be described in detail with reference to examples to aid in understanding the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the following embodiments. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0089]

[0090] <Preparation Example 1: Crushing of Used Lithium-Ion Secondary Battery>

[0091] A discharged cylindrical battery cell was pierced under a nitrogen atmosphere using a nitrogen generator, and then 100 parts by weight of 20°C soft water was added as a solvent per 100 parts by weight of the input cell and wet crushed for 60 minutes to obtain a slurry.

[0092] <Example 1: Recovery of Black Mass from Used Lithium-ion Secondary Batteries>

[0093] In Preparation Example 1 above, the slurry was mixed with a complex aqueous solution of sodium hydroxide, calcium hydroxide, and potassium hydroxide at pH 12. The mixture was prepared such that the slurry and the complex aqueous solution at 80°C had a liquid-to-solid ratio of 1:10, stirred at 300 rpm for 2 hours, and then solid-liquid separation was performed. The separated solid cake was subjected to low-temperature pyrolysis at 400°C for 120 minutes under a nitrogen atmosphere. The pyrolyzed product was classified by sieve vibrating to obtain black mass.

[0094] <Comparative Examples 1 and 2: Recovery of Black Mass from Used Lithium-ion Secondary Batteries>

[0095] The slurry from Preparation Example 1 above was processed under low-temperature pyrolysis conditions in a nitrogen atmosphere without an alkaline thermal hydrolysis step, as shown in Table 4 below. The pyrolyzed product was classified by vibrating sieve to obtain black mass.

[0096] <Test Example 1: Analysis of Components in Black Mass>

[0097] 0.5 g of the black mass obtained in Example 1 and Comparative Examples 1 and 2 was taken, and the valuable metal and impurity components in the black mass were measured using an Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES). The measurement results are shown in Table 5 below.

[0098] Classification Alkaline Thermal Hydrolysis Conditions Low-Temperature Thermal Hydrolysis Conditions Example 1: pH 12, 80℃, sap-to-liquid ratio 1:10, 400℃, 120 min Comparative Example 1: 400℃, 120 min Comparative Example 2: 700℃, 120 min

[0099] Classification Black Mass Composition Content (ppm) Ni, Co, Mn Total Li Impurity Total AlSi Example 1 344 4,900 31,000 42,340 4,570 1,790 Comparative Example 1 349,800 35,400 78,980 20,010 4,840 Comparative Example 2 358,900 37,200 105,100 45,590 9,820

[0100] Referring to Table 5, it can be confirmed that the impurity content in the black mass recovered according to the present invention (Example 1) is 50,000 ppm or less, and that Al, Si, and impurities are significantly removed during the alkaline thermal hydrolysis step. In addition, in Comparative Example 2, where the low-temperature thermal decomposition condition was 700°C, Al, Si, and impurities increased rapidly, which can be expected to be due to the acceleration of phase changes of the metal components.

[0101]

[0102] <Preparation Example 2: Preparation of Low-Purity Black Mass>

[0103] A low-purity black mass was prepared with a total of 200,000 ppm or less of non-transition metal components, including lithium, nickel, cobalt, and manganese.

[0104] <Example 2: Recovery of Black Mass from Low-Purity Black Mass>

[0105] In Preparation Example 2 above, low-purity black mass was mixed with a complex aqueous solution of sodium hydroxide, calcium hydroxide, and potassium hydroxide at pH 12. The mixture was prepared by mixing the low-purity black mass with the complex aqueous solution at 80°C at a liquid-to-soil ratio of 1:10, stirring at 300 rpm for 2 hours, and then separating the solid and liquid phases. The separated solid cake was subjected to low-temperature pyrolysis at 400°C for 120 minutes under a nitrogen atmosphere. The pyrolyzed product was classified by sieve vibrating to obtain black mass.

[0106] <Comparative Examples 3 to 5: Recovery of Black Mass from Low-Purity Black Mass>

[0107] In the same process as in Example 2, the process was carried out by changing the alkaline thermal hydrolysis conditions as shown in Table 6 below. The pyrolyzed product was classified by vibrating sieve to obtain black mass.

[0108] <Test Example 2: Analysis of Components in Black Mass>

[0109] 0.5 g of low-purity black mass and black mass obtained in Example 2 and Comparative Examples 3 to 5 were taken, and the valuable metal and impurity components in the black mass were measured using an inductively coupled plasma spectrometer. The measurement results are shown in Table 7 below.

[0110] Classification Alkaline Thermal Hydrolysis Conditions Low-Temperature Thermal Hydrolysis Conditions Example 2 pH 12, 80℃, ore-liquid ratio 1:10, 400℃, 120 mins Comparative Example 3 pH 12, 80℃, ore-liquid ratio 1:5, 400℃, 120 mins Comparative Example 4 pH 12, 25℃, ore-liquid ratio 1:10, 400℃, 120 mins Comparative Example 5 pH 12, 25℃, ore-liquid ratio 1:5, 400℃, 120 mins

[0111] Classification Black Mass Composition Content (ppm) Ni, Co, Mn Total Li Impurities Total AlSi Low Purity Black Mass 258,200 30,600 115,200 40,840 8,140 Example 2 265,900 28,500 41,300 10,380 2,060 Comparative Example 3 265,600 29,900 45,700 12,130 3,140 Comparative Example 4 261,400 28,100 49,800 18,880 5,170 Comparative Example 5 253,400 29,800 55,900 20,280 6,310

[0112] Referring to Table 7, it can be seen that the impurity content in the black mass recovered according to the present invention (Example 2) is 50,000 ppm or less, and that Al, Si, and impurities are removed by more than 50% compared to low-purity black mass.

[0113] The present invention relates to a method for recovering high-purity black mass from a used lithium-ion secondary battery, and more specifically, to a method for recovering high-purity black mass through an alkaline thermal hydrolysis step in which impurities contained in the crushed cell material are dissolved and separated into the aqueous solution by stirring the crushed cell material in an alkaline aqueous solution, and a low-temperature thermal decomposition step in which organic compound components such as organic binders are decomposed and removed.

[0114] According to the present invention, after crushing the used lithium-ion secondary battery as described above, a method can be provided to effectively dissolve and separate impurity factors that adversely affect recycling efficiency from the used lithium-ion secondary battery using an alkaline thermal hydrolysis method to recover high-purity black mass.

Claims

1. A method for recovering high-purity black mass containing lithium (Li) and transition metal compounds such as nickel (Ni), cobalt (Co), manganese (Mn), copper (Cu), iron (Fe), and chromium (Cr), or one or more transition metals, from a used lithium-ion secondary battery cell or a component including the same, (a) A discharge disassembly step of electrically discharging a used lithium-ion secondary battery cell or a component including the same and disassembling it into a final cell form; (b) A deposition step of completely discharging the finally decomposed cell in an inert atmosphere by forming a penetration hole with a tool such as an electric drill or piercing; (c) A wet crushing step in which a polar protic solvent, such as water, is mixed and crushed in the cell after the above deposition step to solute the ionic substance within the cell and obtain it in the form of a slurry; (d) an alkaline thermal hydrolysis step of stirring the above slurry in an alkaline aqueous solution at a temperature of 20°C to 90°C to dissolve and separate impurities contained in the slurry into the aqueous solution; (e) A solid-liquid separation step in which the aqueous solution obtained after the alkaline thermal hydrolysis step is filtered to separate it into a liquid phase in which impurities are dissolved and a solid cake in which impurities are removed; (f) a low-temperature pyrolysis step of maintaining the above solid cake in an inert atmosphere at a temperature of 200°C to 450°C for 30 to 200 minutes to obtain a powder form in which organic compound components, such as organic binders, are decomposed and removed; (g) A classification step of separating and recovering black mass by vibrating the powder above; Includes, A method for recovering high-purity black mass from a used lithium-ion secondary battery cell or a component including the same, characterized by reusing the liquid containing impurities filtered in the (e) solid-liquid separation step as process water in the (c) wet crushing step.

2. In Paragraph 1, The above-mentioned used lithium-ion secondary battery cell or component including the same includes medium-to-large lithium-ion secondary battery cells, modules, packs, and small lithium-ion secondary battery cells, and The slurry obtained in the above (c) wet crushing step or the low-purity black mass introduced into the above (d) alkaline thermal hydrolysis step is characterized by having a total inorganic component other than transition metals such as lithium, nickel, cobalt, and manganese of 200,000 ppm or less. The high-purity black mass separated and recovered through the above (g) classification step has a total inorganic component other than transition metals such as lithium, nickel, cobalt, and manganese of 50,000 ppm or less, The above slurry or the above low-purity black mass is in powder form LiNi x Co y Mn 1-x-y O2(; here 0 <x<1, 0<y<1)의 리튬니켈코발트 망간산화물을 포함하며, A method for recovering high-purity black mass, characterized in that the impurities separated by dissolution through the above (d) alkaline thermal hydrolysis step include inorganic components other than transition metals such as lithium, nickel, cobalt, and manganese, and organic compounds such as organic binders.

3. In Paragraph 1, A method for recovering high-purity black mass, characterized in that the above (a) discharge decomposition step discharges the residual voltage in a used lithium-ion secondary battery to 15% to 30% using a separate discharger.

4. In Paragraph 1, The above (b) penetration step includes using a gas capable of suppressing oxidative explosion reactions, such as argon (Ar) and nitrogen (N2), and The above-mentioned penetration step of the disassembled cell is performed using a separate penetration jig, and the number of penetration holes per cell by the separate penetration jig is 2 to 20. A method for recovering high-purity black mass, characterized by including supplying the above gas with a purity of 95% to 99.5% at a flow rate of 10 N㎥ / h to 50 N㎥ / h.

5. In Paragraph 1, The above (c) wet crushing step comprises crushing to a size of 0.2 mm to 2.0 mm using one or more of a shredder, cut crusher, and hammer crusher by applying a crushing mechanism of shear and impact according to the shape of the cell, and the polar protic solvent comprises water, characterized in that the method for recovering high-purity black mass.

6. In Paragraph 1, The above (d) alkaline thermal hydrolysis step uses a strongly alkaline aqueous solution with a pH of 10 to 14, and the impurities dissolved by thermal hydrolysis in the alkaline aqueous solution include one or more of aluminum (Al), copper (Cu), iron (Fe), phosphorus (P), fluorine (F), and silicon (Si) compounds, which are byproducts of the anode material and cathode material and electrolyte components that are constituents of the cell. A method for recovering high-purity black mass, characterized in that the alkaline aqueous solution comprises one or more strong alkaline substances such as sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2), and potassium hydroxide (KOH), and the ratio of the slurry to the alkaline aqueous solution is used to be 1:3 to 1:

20.

7. In Paragraph 1, The above (e) solid-liquid separation step is characterized by using a device for separating solid and liquid phases, such as a centrifuge, a filter press, and a vacuum filter, to separate the liquid phase containing impurities including one or more of aluminum, phosphorus, fluorine, and silicon compounds into a solid phase cake containing one or more of transition metal compounds such as lithium, nickel, cobalt, manganese, copper, iron, and chromium, in a method for recovering high-purity black mass.

8. In Paragraph 1, The above (f) low-temperature pyrolysis step includes using a gas capable of suppressing oxidative explosion reactions, such as argon (Ar) and nitrogen (N2), in a rotary kiln, and The above rotary kiln is rotated at an angle of 5 to 30 degrees at a speed of 3 rpm to 30 rpm, and the above gas with a purity of 99% to 99.5% is supplied at a flow rate of 10 N㎥ / h to 80 N㎥ / h, and A method for recovering high-purity black mass, characterized by facilitating the separation of active materials from aluminum and copper current collectors or decomposing and removing organic compound components such as organic binders.

9. In Paragraph 1, The above (g) classification step utilizes a sieve vibrator and a standard sieve, and A method for recovering high-purity black mass, characterized by vibrating the black mass through standard sieves of 20 mesh to 50 mesh for a time of 10 min to 20 min with an amplitude of 0.5 mm to 1.0 mm, and vibrating the black mass through standard sieves of 60 mesh to 120 mesh for a time of 10 min to 20 min with an amplitude of 1.0 mm to 2.0 mm.

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